What are welding parameters:
A very important parameter in the operation of the welding machine, regardless of its device, is the duration of switching on (PV) at different values of the welding current.
Therefrom different manufacturers have different techniques of measurements. The European standard EN 60974-1 takes into account the duration of welding at a temperature of 40 °C until the first stop of the welding machine from overheating, and the PV is calculated based on the ratio of this time to the 10-minute working cycle.
Under more realistic conditions, according to the method of the Italian company Telwin (t = 20 °C, work with interruptions), the number of electrodes that can be used during this period of time is taken into account first of all.
Of course, the PV calculated according to the second method is noticeably higher, and when choosing a device, it is necessary to specify exactly how it was calculated.
However, in the process of operation, it is rarely necessary to burn several electrodes in a row at full power without interruption, and the device with a declared “European” PV of 10-20 % will work until the shutdown as much as with a 60-80% PV calculated according to the “Telvin” method.
An important parameter and the first thing that is usually paid attention to is the range of changes in the welding current.
It indirectly indicates the power of the device. The larger it is, the larger the electrode can be installed and the larger the PV will be when working with small electrodes at equal current strength.
For household purposes and work with a running 3-millimeter electrode, all types of transformers more than have a maximum power of 150 A, for inverters-even less, at this current they calmly cook “four”.
It should be borne in mind that the box with the electrodes usually indicates the recommended currents when working with transformers or rectifiers, the inverter can already cut metal at such currents.
Another important parameter is the idle current. It can be in the range of 60-85 V: the higher, the easier it is to light the arc.
Some models of welding machines are able to function together with devices for argon welding, and models that work in semi-automatic mode (wire welding) are also available.
For domestic use, they are not very interesting — such options are rarely required, and their cost is much higher than that of simple models.
But if you plan to work at a professional level with various types of metals and thin sheets, these functions will be very useful.
Types of welding:
Manual arc welding with a melting electrode (MMA). This is the most popular type of welding, in which the role of the electrode is played by a wire coated with a coating.
During the melting process, the wire connects the parts to be welded, and the coating (slag) protects the weld pool from the effects of oxygen, also contributing to the improvement of the arc characteristics and the quality of the seam.
Most often, ferrous metals, cast iron and some types of non-ferrous metals and alloys are welded in this way, but it is quite difficult to achieve a good connection in the latter case: the low-melting components of the alloys burn out, and the connection is not too high-quality.
Manual welding in a protective gas environment (TIG). Most often, argon with a small admixture of oxygen is used as a gas to burn out dirt and oxides during operation, and welding is carried out with non-consumable graphite or tungsten electrode.
As an additive, rods made of the same material as the parts to be welded are used. The quality of the weld with this method is very high, low-melting alloy components and alloying additives do not burn out, the welding bath is protected from oxygen in the air, the formation of slag is practically excluded.
Welding is almost always performed on a direct current of direct polarity, only for aluminum, alternating current or reverse polarity is more suitable: this way the oxide film is better destroyed.
Despite the fact that this method is quite expensive and does not have a high speed of work, it is quite popular and sometimes indispensable for welding any metals in the case of small amounts of work or if it is not possible to automate the process for various reasons.
In this case, the role of the electrode is usually a welding wire, which is automatically fed into the welding zone, although welding with a non-consumable electrode is also possible.
The device is moved manually. Welding is performed by direct or pulsed current, there is a distinction between welding in an environment of inert (MIG) or active (MAG) protective gases and welding with cored wire — then gas is not required.
For large volumes of deposited metal, MMA welding is more appropriate. The scope of work of semi-automatic machines is the welding of thin sheets, high-alloy steels, non-ferrous metals, as well as industrial applications.
Other welding methods and techniques:
In addition to the three main welding methods listed above, others are also used, especially in industrial production. We will briefly describe some of them.
The source of heat here is a plasma jet obtained by ionization of the working gas between the electrodes, one of which can be the product being welded, or both electrodes are located in a plasma torch.
Both of these methods are used in industrial production more often for surfacing and cutting than for welding itself.
In this case, the connected workpieces or their touching areas are pressed against each other, heated by electricity to a state of plastic deformation, and then further compressed. Among a large number of types of contact welding, you can distinguish spot, butt, relief, and seam welding.
In spot welding, the parts to be welded overlap , are clamped between two electrodes, and then a current pulse of small voltage (several volts) and significant force, up to several thousand amperes, is turned on.
Thus, a welding point is formed between the parts, or two at once, if the electrodes are supplied on one side, and a conductive lining is placed on the other.
Contact welding requires good surface preparation, is suitable for many metals and alloys, and is especially popular for welding thin sheets. The warping of the sheets is low, and the quality (with proper welding parameters) is also high.
This is how, for example, car bodies are assembled in a factory. The method lends itself well to automation, but can also be used in manual mode.
The welding process is accompanied by a large number of dangerous and harmful factors: the high temperature of the hot metal and slag, the bright glow of the arc in the visible, infrared and ultraviolet ranges, the release of toxic gases and aerosols.
When working with electrical devices, failure to comply with the safety regulations is fraught with the risk of electric shock. Therefore, it is necessary to take care of the purchase of a mask and protective clothing.
Welding mask or shield:
This is the most necessary element designed to protect the eyes and face. It is most often made of plastic or electric cardboard (fiber). The shield has to be held with one hand, the mask is attached to the head.
The design of the filter according to GOST must include a protective glass and a Plexiglas substrate. As a filter, either a darkened glass or a “chameleon” filter is used, which automatically darkens when an arc occurs.
“Chameleon” is much more convenient, but also costs more. Depending on the welding conditions, glasses of various degrees of darkening are used, in the “chameleon” it is almost always regulated.
For difficult working conditions, masks are made with breathing filters or an external air supply system, as well as with the possibility of attaching a helmet and headphones.
Clothing and other protective equipment:
Clothing and gloves should be made of low-burning and non-smoldering fabrics such as tarpaulins, rubberized materials or leather. Shoes are also desirable “rougher”, because in addition to sparks and drops of metal, you can accidentally drop a piece of iron on your foot.
The most practical for this purpose are boots made of thick leather or rubber boots. All clothing should be buttoned and fitted in such a way as to prevent the ingress of molten metal droplets into its folds and protect all areas of the skin from the harmful effects of the welding arc. To ensure electrical safety, mats made of rubber or similar dielectric materials are used.
Do not forget also about other means of protection — the serviceability of the equipment, the presence of grounding, reliable fixation of the welding wires in the device and the integrity of their insulation, reliable electrical contact of the return wire on the parts, etc.
Finally, do not lose sight of the reliable fastening of the welded parts. If you properly organize the workplace and work according to your capabilities and without haste, then both the work and the result will only please.